When you need to change number of guests or add a payment to existing reservation you can use LLT_ResUpdateRQ call.
Request sample
<LLT_ResUpdateRQ PrimaryLangID="eng" AltLangID="" Version="1.003">
<HotelReservations>
<HotelReservation>
<UniqueID ID="425054"/>
<RoomStays>
<RoomStay>
<GuestCounts>
<GuestCount AgeQualifyingCode="10" Count="3"/> // Adult
<GuestCount AgeQualifyingCode="8" Count="1"/> // Child
</GuestCounts>
<TPA_Extensions>
<Payments>
<Payment Amount="1000.00">Credit Card (added w/o processing)</Payment>
<Payment ProcessAmount="1.00">Credit Card (added with processing)</Payment>
</Payments>
</TPA_Extensions>
</RoomStay>
</RoomStays>
<ResGlobalInfo>
<Guarantee>
<GuaranteesAccepted>
<GuaranteeAccepted>
<PaymentCard SeriesCode="321" CardNumber="4111111111111202" ExpireDate="2012">
<CardHolderName>Card Holder</CardHolderName>
<Address>
<AddressLine>Some Address-Line 32 1</AddressLine>
<CityName>City</CityName>
<County>US</County>
<PostalCode>555555</PostalCode>
<StateProv></StateProv>
</Address>
</PaymentCard>
</GuaranteeAccepted>
</GuaranteesAccepted>
</Guarantee>
</ResGlobalInfo>
</HotelReservation>
</HotelReservations>
</LLT_ResUpdateRQ>
Required fields:
PrimaryLangID – OTA requires it
UniqueID
GuestCount and/or Payment
Response sample
<LLT_ResUpdateRS>
<HotelReservations>
<Result>Success</Result>
<HotelReservations/>
<HotelReservation CreateDateTime="2020-09-04 09:45:51" ResStatus="Reserved"> // Status might be Reserved OR Tentative.
<POS>
<Source>
<BookingChannel>
<CompanyName Code="resboard_direct">ColibriPMS.com</CompanyName>
</BookingChannel>
</Source>
</POS>
<UniqueID Type="14" ID="425054"/>
<RoomStays>
<RoomStay SourceOfBusiness="ColibriPMS.com">
<RoomRates>
<RoomRate RoomTypeCode="C_2654" RatePlanCode="1799" NumberOfUnits="1" InvBlockCode="0">
<Rates>
<Rate UnitMultiplier="3" RateTimeUnit="Night" EffectiveDate="2022-05-10" ExpireDate="2022-05-13">
<Base AmountAfterTax="1950.40" CurrencyCode="EUR"/>
</Rate>
</Rates>
</RoomRate>
</RoomRates>
<GuestCounts IsPerRoom="1">
<GuestCount AgeQualifyingCode="10" Count="3"/> // Guest count match the number of guests you set in request
<GuestCount AgeQualifyingCode="8" Count="1"/>
</GuestCounts>
<TimeSpan Start="2022-05-10" End="2022-05-13"/>
<Total AmountAfterTax="5851.20" CurrencyCode="EUR">
<Taxes>
<Tax Code="608" Amount="360.00" CurrencyCode="EUR">
<TaxDescription>
<Text>VAT 6%</Text>
</TaxDescription>
</Tax>
<Tax Code="606" Amount="24.00" CurrencyCode="EUR">
<TaxDescription>
<Text>Municipal</Text>
</TaxDescription>
</Tax>
</Taxes>
</Total>
<TPA_Extensions>
<Payments>
<Payment Amount="100.00" CurrencyCode="EUR">Deposit</Payment> // Existing payment from guest folio
<Payment Amount="1000.00" CurrencyCode="EUR">Credit Card (via kiosk)</Payment> // Payment you just added via request
</Payments>
<BalanceDue AmountAfterTax="5573.60" CurrencyCode="EUR"/> // Current balance due
<AllowedGuestCounts> // Number of guests allowed for this room
<AllowedGuestCount Type="MinAdult" Value="0"/>
<AllowedGuestCount Type="NormalAdult" Value="3"/>
<AllowedGuestCount Type="MaxAdult" Value="3"/>
<AllowedGuestCount Type="NormalChildren" Value="0"/>
<AllowedGuestCount Type="MaxChildren" Value="0"/>
</AllowedGuestCounts>
</TPA_Extensions>
<BasicPropertyInfo HotelCode="2651" ChainCode="233" BrandCode="Freedom Serviced Apartments, Lda."/>
</RoomStay>
</RoomStays>
<ResGuests>
<ResGuest ResGuestRPH="1">
<Profiles>
<ProfileInfo>
<UniqueID ID="357116"/> // This is Guest ID, not reservation ID
<Profile>
<Customer>
<Address>
<CountryName Code="US"/>
</Address>
<PersonName>
<GivenName>John</GivenName>
<Surname>Smith</Surname>
</PersonName>
<Email>email@example.com</Email>
<Telephone PhoneNumber="11238890000"/>
</Customer>
</Profile>
</ProfileInfo>
</Profiles>
</ResGuest>
</ResGuests>
</HotelReservation>
</HotelReservations>
</LLT_ResUpdateRS>
Response with an error sample
<LLT_ResUpdateRS xmlns="http://www.opentravel.org/OTA/2003/05"> <Errors> <Error>Credit card number invalid. (20070)</Error> </Errors> </LLT_ResUpdateRS>