Tarehe ya bili iko katika kipindi cha bili.

This is because Swahili links nouns with agreement words that depend on the noun class of the first noun.

• tarehe belongs to a noun class that uses ya
• kipindi belongs to a noun class that uses cha

So:

• tarehe ya bili = date of billing / billing date
• kipindi cha bili = period of billing / billing period

A native English speaker often expects one word like of for both, but in Swahili the connector changes to match the noun class.

Iko means something like it is located / it is found / it is in.

In this sentence, it shows where the billing date falls:

• Tarehe ya bili iko katika kipindi cha bili
• literally: The billing date is in the billing period

So iko is not just a plain equals-sign type of is. It has a sense of position or location.

Swahili often uses ni when one thing is being directly identified as another:

• Huyu ni mwalimu = This is a teacher

But when talking about location or where something is situated, Swahili commonly uses forms like iko:

• Kitabu kiko mezani = The book is on the table
• Tarehe ya bili iko katika kipindi cha bili = The billing date is within the billing period

So here, the sentence is about where the date falls, not about defining what it is.

Katika means in, within, inside, during, depending on context.

In this sentence, katika kipindi cha bili means:

• in the billing period
• or more naturally, within the billing period

It is a very common preposition in Swahili. In some contexts, speakers may also use other expressions such as ndani ya, but katika is perfectly normal here.

Here, kipindi means period or time period.

So kipindi cha bili means billing period.

A useful thing to know is that kipindi can have other meanings in other contexts, such as:

• a period of time
• a session or class period
• an episode of a show

But in this sentence, it clearly means a time span related to billing.

Yes. Bili is a borrowed word, ultimately from English bill.

In modern Swahili, bili is commonly used for:

• a bill
• an invoice
• a statement of charges

So both tarehe ya bili and kipindi cha bili use the same noun bili to mean something related to billing.

Swahili does not normally use articles like English the or a/an.

So a phrase like tarehe ya bili can mean:

• a billing date
• the billing date

The exact meaning depends on context. If the learner has already been shown the meaning as the billing date, that comes from the situation, not from a separate word in the Swahili sentence.

Yes, it is very normal.

The structure is:

• Tarehe ya bili = subject
• iko = verb
• katika kipindi cha bili = prepositional phrase showing location

So the sentence follows a straightforward pattern:

• subject + verb + location

That makes it quite similar to English in structure, even though the noun-linking patterns are different.

More or less, yes:

• Tarehe = date
• ya = of
• bili = bill / billing
• iko = is located / is
• katika = in / within
• kipindi = period
• cha = of
• bili = bill / billing

A very literal version would be:

• Date of bill is within period of billing

That sounds unnatural in English, so a better natural translation is something like:

• The billing date is within the billing period

Yes. Swahili often allows more than one natural wording. For example, someone might say:

• Tarehe ya bili iko ndani ya kipindi cha bili

This also means The billing date is within the billing period.

The difference is small:

• katika = in / within
• ndani ya = inside / within

In your original sentence, katika is clear and standard.