diff --git a/src/main/kotlin/no/nav/syfo/api/maxdate/SykepengerMaxDateRest.kt b/src/main/kotlin/no/nav/syfo/api/maxdate/SykepengerMaxDateRest.kt
index 06b1be0b2..97d3974f9 100644
--- a/src/main/kotlin/no/nav/syfo/api/maxdate/SykepengerMaxDateRest.kt
+++ b/src/main/kotlin/no/nav/syfo/api/maxdate/SykepengerMaxDateRest.kt
@@ -19,11 +19,24 @@ fun Route.registerSykepengerMaxDateRestApi(
     get("/api/v1/sykepenger/maxdate") {
         val principal: BrukerPrincipal = call.authentication.principal()!!
         val sykmeldtFnr = principal.fnr
+        val isoFormat = call.request.queryParameters["isoformat"]?.toBoolean() ?: false
 
         try {
             val sykepengerMaxDate = sykepengerMaxDateService.getSykepengerMaxDate(sykmeldtFnr)
-            val maxDate = sykepengerMaxDate?.let { formatDateForLetter(it.forelopig_beregnet_slutt) }
-            val utbetaltTom = sykepengerMaxDate?.let { formatDateForLetter(it.utbetalt_tom) }
+            val maxDate = sykepengerMaxDate?.let {
+                if (isoFormat) {
+                    it.forelopig_beregnet_slutt.toString()
+                } else {
+                    formatDateForLetter(it.forelopig_beregnet_slutt)
+                }
+            }
+            val utbetaltTom = sykepengerMaxDate?.let {
+                if (isoFormat) {
+                    it.utbetalt_tom.toString()
+                } else {
+                    formatDateForLetter(it.utbetalt_tom)
+                }
+            }
             log.info("Fetched sykepengerMaxDate from database: ${sykepengerMaxDate?.forelopig_beregnet_slutt}")
             call.respond(SykepengerMaxDateResponse(maxDate, utbetaltTom))
         } catch (e: Exception) {