diff --git a/pain.go b/pain.go
new file mode 100644
index 0000000..98ec0a2
--- /dev/null
+++ b/pain.go
@@ -0,0 +1,147 @@
+package sepa
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+var (
+	SEPARegexps = map[string]*regexp.Regexp{
+		"MsgId":            RestrictedIdentificationSEPA1,
+		"CreDtTm":          ISODateTime,
+		"NbOfTxs":          Max15NumericText,
+		"CtrlSum":          RestrictedDecimalNumber,
+		"Nm":               Max70Text,
+		"PmtInfId":         RestrictedIdentificationSEPA1,
+		"PmtMtd":           PaymentMethod2Code,
+		"PmtMetaSvcLvl":    ServiceLevelSEPACode,
+		"PmtMetaLclInstrm": LocalInstrumentSEPACode,
+		"SeqTp":            SequenceType1Code,
+	}
+)
+
+type PainXML struct {
+	GroupHeader            GrpHdr   `xml:"GrpHdr"`
+	PaymentInformation     []PmtInf `xml:"PmtInf"`
+	TransactionInformation []TxInf  `xml:"DrctDbtTxInf"`
+}
+
+func (p *PainXML) Valid() error {
+	var err []string
+	if e := p.GroupHeader.Valid(); e != nil {
+		err = append(err, fmt.Sprintf("%v", e))
+	}
+	if len(p.PaymentInformation) < 1 {
+		err = append(err, "no payment information")
+	}
+	if len(p.TransactionInformation) < 1 {
+		err = append(err, "no transaction information")
+	}
+
+	if len(err) > 0 {
+		return fmt.Errorf("pain XML not valid: %v", strings.Join(err, ", "))
+	}
+
+	return nil
+}
+
+type GrpHdr struct {
+	MessageId       string   `xml:"MsgId"`
+	Timestamp       string   `xml:"CreDtTm"`
+	NumTx           string   `xml:"NbOfTxs"`
+	Sum             string   `xml:"CtrlSum"`
+	InitiatingParty InitgPty `xml:"InitgPty"`
+}
+
+func (g *GrpHdr) Valid() error {
+	var err []string
+	if !SEPARegexps["MsgId"].MatchString(g.MessageId) {
+		err = append(err, "msgId did not match expected format")
+	}
+	if !SEPARegexps["CreDtTm"].MatchString(g.Timestamp) {
+		err = append(err, "timestamp did not match expected format")
+	}
+	if !SEPARegexps["NbOfTxs"].MatchString(g.NumTx) {
+		err = append(err, "numtx did not match expected format")
+	}
+	if !SEPARegexps["CtrlSum"].MatchString(g.Sum) {
+		err = append(err, "sum did not match expected format")
+	}
+	// TODO
+	/*
+		if g.InitiatingParty == nil {
+			err = append(err, "no initiating party found")
+		} else {
+			if !SEPARegexps["Nm"].MatchString(g.InitiatingParty.Name) {
+				err = append(err, "initiating party's name did not match expected format")
+			}
+		}
+	*/
+
+	if len(err) > 0 {
+		return fmt.Errorf("group header not valid: %v", strings.Join(err, ", "))
+	}
+	return nil
+}
+
+type PmtInf struct {
+	Id          string   `xml:"PmtInfId"`
+	Method      string   `xml:"PmtMtd"`
+	PaymentMeta PmtTpInf `xml:"PmtTpInf"`
+}
+
+func (pmt *PmtInf) Valid() error {
+	var err []string
+	if !SEPARegexps["PmtInfId"].MatchString(pmt.Id) {
+		err = append(err, "payment info id does not match expected format")
+	}
+	if !SEPARegexps["PmtMtd"].MatchString(pmt.Method) {
+		err = append(err, "payment info id does not match expected format")
+	}
+	if e := pmt.PaymentMeta.Valid(); e != nil {
+		err = append(err, fmt.Sprintf("payment meta not valid: %v", e))
+	}
+
+	if len(err) > 0 {
+		return fmt.Errorf("payment info (Id: %q) not valid: %v", pmt.Id, strings.Join(err, ", "))
+	}
+	return nil
+}
+
+type PmtTpInf struct {
+	ServiceLevel    Code   `xml:"SvcLvl"`
+	LocalInstrument Code   `xml:"LclIntrm"`
+	SequenceType    string `xml:"SeqTp"`
+}
+
+type Code struct {
+	Code string `xml:"Cd"`
+}
+
+func (meta *PmtTpInf) Valid() error {
+	var err []string
+	// TODO: check meta.ServiceLevel for nil
+	if !SEPARegexps["PmtMetaSvcLvl"].MatchString(meta.ServiceLevel.Code) {
+		err = append(err, "incorrect service level present (must be 'SEPA')")
+	}
+	// TODO: check meta.LocalInstrument for nil
+	if !SEPARegexps["PmtMetaLclInstrm"].MatchString(meta.LocalInstrument.Code) {
+		err = append(err, "incorrect local instrument present")
+	}
+	if !SEPARegexps["SeqTp"].MatchString(meta.SequenceType) {
+		err = append(err, "sequence type has incorrect format")
+	}
+
+	if len(err) > 0 {
+		return fmt.Errorf("payment meta not valid: %v", strings.Join(err, ", "))
+	}
+	return nil
+}
+
+type TxInf struct {
+}
+
+type InitgPty struct {
+	Name string `xml:"Nm"`
+}
diff --git a/pain_regexp.go b/pain_regexp.go
new file mode 100644
index 0000000..d6ae97e
--- /dev/null
+++ b/pain_regexp.go
@@ -0,0 +1,19 @@
+package sepa
+
+import (
+	"regexp"
+)
+
+var (
+	ISODateTime                   = regexp.MustCompile(`\d{4}(-\d\d){2}T\d\d(:\d\d){2}`)
+	RestrictedIdentificationSEPA1 = regexp.MustCompile(`([A-Za-z0-9]|[\+|\?|/|\-|:|\(|\)|\.|,|'| ]){1,35}`)
+	RestrictedIdentificationSEPA2 = regexp.MustCompile(`([A-Za-z0-9]|[\+|\?|/|\-|:|\(|\)|\.|,|']){1,35}`)
+	Max15NumericText              = regexp.MustCompile(`[0-9]{1,15}`)
+	RestrictedDecimalNumber       = regexp.MustCompile(`[+-]\d+\.\d\d`)
+	Max70Text                     = regexp.MustCompile(`.{1,70}`)
+
+	ServiceLevelSEPACode    = regexp.MustCompile(`SEPA`)
+	SequenceType1Code       = regexp.MustCompile(`FRST|RCUR|FNAL|OOFF`)
+	PaymentMethod2Code      = regexp.MustCompile(`DD`)
+	LocalInstrumentSEPACode = regexp.MustCompile(`CORE|B2B`)
+)