Endeks faturayla uyuşmadığı takdirde sayaç okuması ve tüketim dönemi incelenecek.

Literally, yes: endeks is a borrowing related to index. But in utility/billing language, it usually means the meter index/value shown on the meter, not an index in the stock-market or general-data sense.

So here endeks refers to the meter’s recorded number/figure.

It is a formal way to say if it does not match or in the event that it does not match.

• uyuşmak = to match, correspond, agree
• uyuşmadığı = that it does not match
• takdirde = in the case that / if

Together, uyuşmadığı takdirde is a common formal written pattern in notices, contracts, and official customer-service language.

Both can express if it doesn’t match, but they are different in tone.

• uyuşmazsa = shorter, more everyday
• uyuşmadığı takdirde = more formal, bureaucratic, written

So the sentence sounds like official service or billing language rather than casual speech.

Because uyuşmak does not take a direct object the way English match sometimes seems to.

In Turkish, uyuşmak commonly goes with -le / -la / ile, meaning with:

• faturayla uyuşmak = to match with the bill

So:

• fatura + ile → faturayla
• literally: with the bill

Using faturayı would suggest a direct object, which is not how uyuşmak normally works here.

The y is a buffer consonant.

When ile is attached to a noun ending in a vowel, Turkish usually inserts y:

• fatura + ile → faturayla
• masa + ile → masayla

So faturayla is the attached form of fatura ile.

It breaks down like this:

• uyuş- = match, agree
• -ma- = negation
• -dık = a verbal noun/participle ending
• -ı = third-person possessive/agreement element

So uyuşmadığı literally means something like its not matching or that it does not match.

In this sentence, that whole form is used before takdirde to make a formal conditional expression.

Because endeks is the subject of the conditional part, and Turkish often leaves subjects in the basic form with this kind of structure.

So:

• Endeks faturayla uyuşmadığı takdirde = If the index does not match the bill

There is no special extra marking needed on endeks here.

It is a noun compound, often called an izafet structure in Turkish grammar.

• sayaç = meter
• okuma = reading
• okuması = its reading / the reading of the meter

So sayaç okuması means meter reading.

This is very common in Turkish: one noun modifies another, and the second noun takes a possessive-type ending.

Yes. It is another noun compound.

• tüketim = consumption, usage
• dönem = period
• tüketim dönemi = consumption period / usage period

In a billing context, this is basically the period of consumption being referred to on the bill.

İncelenecek is the future form of the passive verb incelenmek:

• incelemek = to examine
• incelenmek = to be examined
• incelenecek = will be examined

So the sentence is not saying who will do the examining. It simply says that the meter reading and consumption period will be examined.

This is very typical in formal Turkish.

Official notices often prefer the passive because it sounds:

• impersonal
• neutral
• procedural
• more formal

So instead of saying we will examine, Turkish often says it will be examined.

That is especially common in bills, warnings, regulations, and customer-service texts.

Because Turkish does not require plural marking on the verb the way English often does.

With third-person subjects, especially inanimate ones, a singular verb is very normal:

• sayaç okuması ve tüketim dönemi incelenecek

This is completely natural Turkish. You do not need a plural verb ending here.

Yes, to some extent. Turkish word order is flexible, but the verb usually stays near the end.

The original order is very natural for formal writing:

• Endeks faturayla uyuşmadığı takdirde sayaç okuması ve tüketim dönemi incelenecek.

You could also rearrange it for emphasis, for example:

• Sayaç okuması ve tüketim dönemi, endeks faturayla uyuşmadığı takdirde incelenecek.

But the original version sounds like a standard official notice, which is probably why it is written that way.